1. Field of the Invention
This invention relates to an electronic calculator driving and battery pack recharging circuit to conveniently and safely drive an electronic calculator from a supply of dc voltage or from either one of a plurality of disposable batteries or a rechargeable battery pack.
2. Description of the Prior Art
As will be understood by those skilled in the art, there are presently two well known types of battery classifications, primary battery cells and secondary battery cells. Primary battery cells typically cannot be recharged and are discarded after use. Secondary battery cells can be typically recharged for continued reuse many times. The primary battery cells cannot be recharged, inasmuch as primary cells, which are subjected to a voltage charge applied across the terminals thereof, can explode. Thus, conventional electronic calculators which utilize disposable batteries as a source of power are designed so that the rectified output from an ac adapter accessory cannot be placed across the terminals of the primary cells. Moreover, other conventional calculators which utilize rechargeable batteries as a source of power are inconveniently designed so that the secondary cells are not accessible and cannot be easily replaced or repaired by the user. The inconvenient design of conventional calculators occurs as the result of the calculator manufacturers attempt to prevent the user from either intentionally or inadvertently installing disposable primary battery cells in a calculator designed to use only rechargeable secondary battery cells and, consequently, causing possible harm to the user or to the calculator, if the primary battery cells should explode.
In most instances, in order to obtain the advantages offered by both rechargeable battery pack powered and disposable battery powered calculators, two separate calculators must be purchased by the user. Those calculators which have dual primary and secondary battery capabilities require that the user follow special procedures to prevent the possibility of charging the disposable primary battery cells. Consequently, both the cost and the effort required to operate the prior art calculators are undesirably increased.